Cargo handling apparatus



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United States PateiitO CARGO HANDLING APPARATUS Elmer J. Renner, Aurora, [1]., assignor to Stephens- Adamson Mfg. Co., a corporation of Illinois Application October 10, 1955, Serial No. 539,503

15 Claims. (Cl. 214-89) This invention relates to cargo handling apparatus, and more particularly to such a cargo elevator that will receive a moving pallet loaded with cargo and raise it automatically to a predetermined height.

A cargo elevator of this type is especially useful for receiving a load of cargo from a cargo accumulation station and lifting it to within reach of an airplane cargo hold so that it may be loaded into the airplane. The cargo elevator of this invention may be used, for instance, to lift cargo pallets oil an endless conveyor belt and raise them into position for transfer of the cargo to a plane which has been brought into position next to the conveyor belt.

To be adapted for such use, a cargo elevator should operate as nearly fully automatically as possible, in order to free the attention of the baggage men so that they may carry out the irreducible minimum of tasks that must in any event be done manually in any loading or unloading operation. If more than one cargo hold is to be loaded, the cargo elevator for each hold must be so constructed that its operation will not interfere with but, on the contrary, can be coordinated with the operation of the elevators at the other cargo holds. The cargo elevator must be reliable in operation and sturdy of construction, yet not so large as to interfere with either the plane itself or the other baggage handling apparatus such as the endless conveyor belt.

The apparatus of this invention achieves all these aims. The apparatus is comprised of a hoist having switch means for selectively causing the hoist to be raised or lowered, a mobile cargo pallet which carries means to trip said switch automatically when the pallet comes into position to be lifted by the hoist, and means to propel the pallet to the hoist, the propelling means being adapted to be rendered inoperative after the cargo pallet has been raised a predetermined distance.

The invention will be described by reference to the embodiment shown in the accompanying drawings. in the drawings:

Figure l is a diagrammatic perspective view showing one embodiment of the cargo elevator of this invention as it may be used with an airplane to be loaded with cargo;

Figure 2 is a plan view of the inner end of a baggage conveying system of the kind shown in Figure 1;

Figure 3 is a plan view of the outer end of that system;

Figure 4 is a side elevation of the outer end of that system;

Figure 5 is a sectional view of a sealing lip used between adjacent sections of the conveyor belt shown in Figure 2;

Figure 6 is a side elevation of one embodiment of the hoist used in this invention showing the hoist in several positions;

Figure 7 is a plan view of one of the hoists of the system shown in Figure 1;

Figure 8 is a fragmentary side elevation of portions of the hoist and cargo pallet (the latter in phantom) of one embodiment of the cargo elevator of this invention;

2,824,656 Patented Feb. 25, 1958 Figure 9 is an end view of the hoist and cargo pallet comprising one embodiment of the cargo elevator of this invention;

Figure 10 is an end view of the hold-down device employed with said embodiment;

Figure ll is a side elevation of the same device;

Figures 12A and 12B are end elevations of the embodiment of Figure 9 showing the hoist in its elevated positron;

Figure 13 is a sectional view taken along line 13-13 of Figure 24 showing the belt conveyor structure used with the embodiment of the invention shown in Figure 9;

Figures 14A and 14B give a side elevation of the same embodiment as shown in Figures 12A and 128;

Figure 15 is a fragmentary side elevation of the hoist switch means of the same embodiment;

Figure 16 is a plan view of the embodiment shown in Figure 148;

Figure 17 is a fragmentary end elevation showing the switch tripping means of the hoist employed at the outermost plane loading station in the embodiment of the invention shown in Figure 1;

Figure 18 is a plan view of a hoist at the outermost station of the system shown in Figure 1;

Figure 19 is a fragmentary side elevation of the same hoist with a pallet (shown in phantom) upon it;

Figure 20 is an end elevation of the same hoist;

. Figure 21 is a fragmentary plan view of the hoist at the innermost station in the system shown in Figure 1;

Figure 22 is a sectional view taken along line 22--22 of Figure 18;

Figure 23 is a circuit diagram of the hydraulic system employed to raise and lower the hoist of the embodiment shown in Figures 14A and 143;

Figure 24 is a side elevation of the cargo pallet of the embodiment of Figure l, the pallet being shown riding upon the endless conveyor belt;

Figure 25 is a plan view of two cargo pallets upon the conveyor belt;

Figure 26 is an exploded detail view of the traction plate on the bottom side of the pallet of Figure 24; and

Figure 27 is a schematic diagram of the electrical circuits for actuating the hydraulic systems of the cargo hoists of the system shown in Figure 1, including an interlock circuit that connects the electrical circuits of the hoists in that system.

General description of cargo elevator in use The cargo elevator of this invention is shown diagrammatically in Figure 1 as used for handling cargo to be loaded and unloaded from an airplane. Cargo elevators 30, 31 and 32 are shown in position near cargo holds 33, 34 and 35 of airplane 36. The cargo elevator of this invention may also be employed in any other system in which cargo moves to and from the elevator.

In the embodiment shown, cargo elevators 30, 31 and 32 are used with endless conveyor 37. Conveyor 37 leads from a cargo accumulation station (not shown) located at the left and rear of plane 36, to a point just behind the plane, and from there along the right side of the plane to a short distance beyond the nose. Conveyor 37 includes endless conveyor belt 38 leading from the cargo accumulation station, curved endless conveyor belt 39 which changes the direction of conveyor 37, and endless conveyor belt 40 which runs along the side of plane 36. Conveyor 37 also includes tracks 41 on either side of endless conveyor belts 38, 39 and 40.

Items of passenger luggage, freight or air mail may be brought from the cargo accumulation station for loading on plane 36 either upon conveyor belts 38, 39 and 40 or of cargo elevators 30, 31 and 32, respectively. Cargo pallets 45, 46 and 47, while moving from the cargo accumulation station to plane 36, ride upon tracks 41 of conveyor 37.

As will be explained below, cargo pallets 45, 46 and 47 can be sent out to plane 36 on conveyor 37 either loaded with cargo to be delivered to the plane. or in an empty condition for unloading cargo from the plane. When a cargo pallet arrives at its associated cargo hold, it interacts with the rest of the cargo elevator at that location to raise the cargo carried by the pallet toward the hold into which the cargo is to be transferred. By means to be explained below, the operation of any particular one of cargo elevators 30, 31 and 32 to raise the cargo carried by the pallet which is a part of that particular elevator may be made automatic. Cargo elevator is arranged to be actuated only by the arrival of cargo pallet 45, cargo elevator 31 by the arrival of pallet 445 and elevator 32 by the arrival of pallet 47.

Figures 2 and 3 show in plan view the path along which conveyor 37 leads from the cargo accumulation station to plane 36 and along the side of the plane to the forward end of the plane. Conveyor belt 38 approaches plane 36 at the rear of the plane along a path lying at right angles to the longitudinal axis of the plane. Conveyor belt 39 makes a curved right angle turn in the vicinity of the rear of plane 36. Conveyor belt 40 then continues along the side of the plane. Tracks 41 flank the conveyor belts along the entire path. In Figures 2 and 3 conveyor belts 38 and 40 and the associated tracks 4] are broken away to show that the length of conveyor 37 may be adapted to any size airplane and any airport layout.

Hoist 48 of cargo elevator 30 is located, as shown in Figure 2, near the most rearward cargo hold 33 of plane 36. Hoists 49 and 50 of cargo elevators 31 and 32, re spectively, are located at forward cargo holds 34 and 35. Figure 4 shows in side elevation the location of hoists 49 and 50. It also indicates (in broken line) how cargo hoist 50 may be raised from its down or collapsed position (shown in solid line) into its most elevated position.

Figure 5 shows a sealing lip 51 which closes the gap between the ends of conveyor belts 38 and 39 or between belts 39 and 40. For clarity, sealing lip 51 is omitted from Figure 2.

Hoist Figure 6 gives a side elevation of hoist 49 when in its collapsed or down position. The hoist is shown in broken lines in an intermediate position to which it may be raised by actuation of the elevating mechanism of the hoist, and also in broken lines in its uppermost position after it has been fully elevated.

Hoist 49 includes two elevating members 51 and 52 spaced on either side of conveyor 37. The elevating member of hoist 49 which is seen in Figure 6 is member 52. Cargo pallet 46, which is adapted to actuate hoist switch 53 as it depresses cam bar 54 upon passing over elevating member 52, approaches from the left in the drawing shown in Figure 6.

When cam bar 54 is depressed, this operates cam lever 55 which in turn energizes hoist switch 53. When panel 54 is depressed, it pushes down the upper end 56 of cam 55. As the cam is pivoted by rotatable attachment to elevating member 52, the lower end of the cam is caused to rise and push against wheel 57 of limit switch 53.

Limit switch 53 is connected in the electrical circuit of the motor that drives the hydraulic pump for cargo hoist 49. The pump is connected to hydraulic ram 60 on one side of cargo hoist 49, and to ram 60a (shown in Figures 7 and 9) on the opposite side of the hoist. Ram 60 is rotatably attached at its bottom end to base member 61 of cargo hoist 49. Piston 62 extends from the upper end of hydraulic ram 60, and is rotatably attached at its upper end to upright member 63 of hoist 49, located at the rear end of the hoist. In the same 4 way, the bottom end of ram 60a and top end of piston 62a are rotatably attached to base member 61a and upright member 63a, respectively, on the other side of the hoist.

Upright 63 at one end of hoist 49 and upright 64 at the other are pivoted at their lower ends about axles 65 and 66, respectively. These axles are journalled at one end in base member 61, seen in Figure 6. Axles 65 and 66 extend across to the opposite side of hoist 49, where they are journalled in base member 61a and carry pivoted members 63:: and 64a, all corresponding to the similarly numbered members which are seen in Figure 6.

Platform 67 also extends from one side of cargo hoist 49 to the other, serving both to carry the major part of the hydraulic system of the hoist (as explained below) and also to help provide rigidity between base members 61 and 61a on opposite side of the hoist.

Elevating member 52 is supported by uprights 63 and 64, to which it is rotatably attached at either end. Elevating member 51, on the opposite side of cargo hoist 49, is similarly supported by uprights 63a and 640. Cross bars 68 and 680, respectively, reinforce uprights 63 and 64 on one side of the hoist and uprights 63a and 64a on the other. The cross bars are rotatably attached at each end to the uprights they enforce.

The framework of cargo hoist 49 that results from this arrangement of members has the appearance when in its most elevated position of a box frame riding upon two wheel-bearing axles, the frame having no cross pieces at the top, and a wide platform cross member at one end of the bottom. The box frame is collapsible in the direction of the end of the hoist at which hydraulic rams 6t) and 600 are rotatably attached to base members 61 and 61a.

At all stages of collapse of this box frame and later return of the frame to the upright position, the frame maintains (by means described below) its parallelepiped shape. The result is that elevating members 51 and 52 sweep through the same are on both sides of cargo hoist 49, maintaining at all times their parallel relation and their equal heights above the ground.

When hoist switch 53 is closed, the hydraulic pump of hydraulic rams 60 and 60a is caused to operate. This forces pistons 62 and 62a to be moved out of the cylinder of rams 60 and 60a. As seen from the intermediate broken line position of cargo hoist 49 shown in Figure 6, pushing piston 62 out of the cylinder of ram 60 forces upright 63 to rotate at its bottom end about rear axle 65. As upright 63 rises from the collapsed position, cross bar 68 and elevating member 52 pull up through a similar path upright member 64 at the other end of elevating member 52.

As piston 62 is pushed farther out of the cylinder of ram 60 by continued operation of the hydraulic pump of the system, uprights 63 and 64 continue to approach the vertical position until elevating member 5.2 has reached its highest position, which is shown in broken line in Figure 6. At the same time, elevating member 51 is moved up into the same relative position on the other side of the hoist.

As stated above, the first part of the rise of cargo hoist 49 is accomplished automatically upon depression of cam bar 53. The second part of the rise of the hoist is produced (as will be described below) by manual open ation of a switch. When the hoist has reached its ex" treme elevated position, the manual switches are no longer actuated and no additional hydraulic pressure is applied. Since the hydraulic system is fluid tight, the position taken by the hoist is a stable one.

In fact, hoist 49 will remain in any elevated position at which it comes to rest when actuation of the manual switch ceases. The positions to which hoists 48, 49 and 50 are raised depends upon the height of cargo holds 33, 34 and 35 which are being serviced by the hoists.

Cargo heist 49 is shown in Figure 6 as being carried on wheels adapted to ride upon plate 69 and corresponding plate 69a on the other side of the hoist. Within predetermined limits, cargo hoist 49 may be moved forward or backward, as desired. This provides additional flexibility in the use of the apparatus of this invention, for it permits forward and rearward adjustment to be made in the position of cargo hoist 49 depending upon the location, for example, of cargo hold 34 in the plane which is being loaded or unloaded.

As best seen from Figure 9, rear wheel 70 is supplemented in the embodiment shown by other wheels 70a, 70b and 70c, all carried upon axle 65. Similarly, wheel 71 seen in Figure 6 is supplemented by wheels 71a, 71b and 710, all carried by axle 66.

The center of gravity of cargo hoist 49 shifts markedly when upright members 63 and 64 collapse from the vertical position to a near horizontal position and return to the vertical. This shift is made even more marked by addition of the weight of pallet 46 and the cargo it carries when these are raised or lowered upon elevating members 51 and 52. The pallet and its cargo tend to tip hoist 49 forward over front axle 66, raising wheels 70 off the ground at the rear end of the hoist.

One factor opposing the tendency of hoist 49 to tip forward when loaded is the placement of the motor, pump and hydraulic mechanism which operate the hoist. These are for the most part supported upon platform 67 at the rear end of hoist 49. The weight of this equipment helps to counterbalance the shift in center of gravity as the pallet and load are lowered, or as they are first caused to be raised, by elevating members 51 and 52.

Another means of opposing this shift in the center of gravity of the loaded cargo hoist is to place a counterweight of concrete or similar heavy material upon platform 67 at the rear end of hoist 49.

Still another means of counteracting the shift in center of gravity of hoist 49 is to provide a hold-down device which will operate to keep wheels 70, 70a, 70b and 70c from being lifted very far, if at all, off plates 69 and 69a. Such a hold-down device is seen in Figure 9, where bracket 75 is connected to plate 69 at its bottom end and overhangs wheel 70 at the top. Bracket 75 extends along conveyor 37 for the same distance it is desired to move hoist 49 to accommodate different locations of cargo holds of airplanes with which the hoist is used. A similar hold-down device 75a is provided on the opposite side of cargo hoist 49 to help hold down wheel 70c. (Holddown device 75 has been omitted for clarity from Figures 6 and 14A.)

The cargo hoist of this invention may be designed to ride upon rails 76 as shown in Figures 10 and 11 rather than upon plate 69. In this embodiment, there is a pair of flanged wheels 77 on each side of cargo hoist 49. The wheel shown in Figures 10 and 11 is at the left rear end of hoist 49. It occupies, in other words, the same relative position with respect to the cargo hoist as the wheels 70b and 70c shown in Figure 16.

In this embodiment, base member 61a has welded to it angles 78 and 79, which together form a hold-down device which will counteract the upsetting tendency described above. Angles 78 and 79 embrace flange 80 at the top of rail 76 upon which wheels 77 ride. Grasping the bottom part of flange 80 on both sides, angles 78 and 79 keep base member 61a and therefore axle 65 and wheel 77 all in their operative positions, with the wheel riding upon track 76.

Figures 9, 12A and B, 14A and B, and 15 show in more detail how cargo hoist 49 raises cargo pallet 46 into its elevated position. From these figures can be seen the movement by which hydraulic rams 60 and 60a force pistons 62 and 62a into an extended position, thus elevating upright members 63 and 63a until the latter are in a vertical position. As seen from Figures 14A and 148, in this position cross bar 68 and elevating member 52 are horizontal. Elevating members 51 and 52 are both raised, as seen in Figures 12A and 1213, to their eittremd upper position, and they have carried with them cargo pallet 46.

Upright 63 is comprised of two channel members 63 and 6.5" which face each other and are connected by a wide plate 81 at their bottom ends and a second wide plate 62 at their top ends. Members 6.5 and 63" each have a hole at the bottom end through which axle 65 passes. thus the upright member forms a yoke through WHICH the axle tor wheels 70, 700, 700 and 70c passes.

The upper end of hydraulic piston 62 1S rotataoiy attached l0 upright member 63 by means of rod as which is ouinalled in housings 84 and a4" attached to uprights 63' and 63", respectively. Horizontal members 66' and 68" are rotatabiy attached to uprights 6: and 63", respectively, at the rear end of hoist 49 and to toe corresponding upright members at the front end of the hoist.

blevanng member :2 is connected at the top of upright 63 through a construction somewhat similar to the connection or the same upright to axle 65 at the bottom of the hoist. Elevating member 52 is a wide channel member which rides with its open portion facing down ward, so that the sides of the channel overlap the top of upright 63. The top of upright 63 is formed in a yoke somewhat like that at the bottom of the upright. Connecting rod provides a means of rotatably attaching the yoke so formed to the side walls of the channel comprising elevating member 52.

The same type of construction is used for the other three upright members and elevating member 51. The upright members all have a relatively large transverse dimension in comparison to their height. This gives them a degree of stability in a transverse direction which is especially important in a cargo hoist which is used to elevate loads having the weight of cargo pallet 46 and the cargo it carries.

When cargo hoist 49 is in its down or collapsed position with upright members 51 and 52 at a height just flush with tracks 41 and conveyor belt 40, the frame of the hoist has not yet been swung down to the very lowest position it could possibly assume. Hydraulic rams 60 and 60a tend to keep uprights 63 and 63a at the desired angle to the horizontal, atter additional hydraulic pressure is no longer applied to move hoist 49 down to its bottom position. Stop 91, shown in Figure 6, provides an additional, mechanical means of keeping upright 63 at the proper angle when hoist 49 is in its down position. Stop 91a, on the other side of the hoist, does the same for upright 63a. The stops, located about midway be tween the ends of hoist 49, are carried by base members 61 and 61a, respectively.

The construction of cargo hoist 49 is shown in plan view in Figure 7. in that figure, cargo pallet 46 approaches the hoist from the right hand side of the drawing. Conveyor belt 40, flanked by tracks 41, passes between elevating members 51 and 52. Elevating member 52 is supported on upright members 63 and 64, while elevating member 51 is supported on upright members 63a and 64a.

The hoist is shown in Figure 7 in its down or collapsed position. In this position, hydraulic pistons 62 and 620 are withdrawn into the cylinders of hydraulic rams 60 and 60a. When the pistons are extended from the cylinders by application of hydraulic pressure at the bottom end of the cylinders, elevating members 51 and 52 are caused to swing upward in an are from the position they occupy in Figure 7, and as they do so they also move to the right in that drawing.

Hoist switch As shown in Figures 9 and 12B, elevating members 51 and 52 carry guide chutes 92 and 93, respectively. These have been omitted for clarity from Figure 148.

The guide chutes on hoist 49 are located in the middle of the elevating members. Guide chute '92 operates to guide cam roller 94 directly to earn bar 54 as cargo pallet 46 rolls upon elevating members 51 and 52 while cargo hoist 49 is in its down or collapsed position. Guide chute 93 keeps guide roller 95 in the proper transverse position so that cam roller 94 will maintain its correct transverse position for tripping cam bar 54. Cam roller 94 and guide roller 95 are both at the front end of cargo pallet 46. Similar rollers are located in the same positions at the rear of the cargo pallet, but for clarity have been omitted from Figures 9 and 12B.

From Figure 9 it is seen that cam rollers 100 and 101 (shown in phantom) may be carried at the front end of other cargo pallets in positions from which they will selectively actuate other cam bars 102 and 103 located on cargo hoists 50 and 48, respectively. Similarly, guide rollers 104 and 105 may be located in corresponding positions on the other side of cargo pallets 47 and 45, respectively.

In the embodiment shown in Figures 6, 8, 14B and 15, the hoist switch mechanism is for clarity shown on elevating member 52 on the right side of hoist 47 (as the hoist is apprached by cargo pallet 46), rather than on the left side as in Figures 7, 9, 12B and 16 The hoist switch is shown on the left hand side of cargo hoist 50 in Figures 18 and 19, and on the left hand side of cargo hoist 48 in Figure 21. The hoist switch may in fact be located on either side of the cargo hoist, as desired. One advantage of locating the switch on the right hand elevating member (the elevating member which is farther from the plane being loaded or unloaded) is that in this position there is less chance of accidental actuation of the hoist switch by baggage handling personnel, one of whom might inadvertently step upon the cam bar which controls the switch.

Figure 15 shows the position occupied by cam bar 54 as cam roller 94 approaches it when cargo pallet 49 is moved along conveyor 37 by conveyor belt 40. In this position. elevating member 52 is substantially flush horizontally with the top surface of conveyor belt 40. As seen. upright 64 lies in a collapsed position with horizontal member 68 and elevating member 52 depressed accordingly. Figure 8 shows the position occupied by cam bar 54 after it has been depressed.

Cam lever 55 rotates about fulcrum 110 which is attached to elevating member 52. The bottom end of cam lever 55 presses against switch Wheel 57, which is adapted to actuate hoist switch 53. The upper end of cam lever 55 is rotatably attached to earn bar 54 by means of hinge 56.

The other end of cam bar 54 carries adjusting arm 111. which is rotatably attached to the cam bar at its upper end and to elevating member 52 through fulcrum 112 at its lower end. The lower end of adjusting arm 111 extends beyond fulcrum 112 to provide a seating 113 for adiusting bolt 114. Bolt 114 is screwed through arm end 113, with the threaded end of the bolt pressing against adiusting stop 115, which is attached to elevating member 52. As adjusting bolt 114 is screwed into or out of portion 113 of arm 111, this moves portion 113 away from or permits it to move toward stop 115, respectively. The upper end of arm 111 is thus moved down as the arm rotates about fulcrum 112 or is permitted to move higher when cam bar 54 is urged upward by means to be described. By employing adjustment of bolt 114 to lower or raise, as desired, the end of cam bar 54 to which adjusting arm 111 is attached, the distance cam bar 54 must be depressed before switch 53 is actuated can be varied, and thus the rapidity of response of the hoist switch to arrival of cargo pallet 46 can be controlled.

Cam bar 54 is supported in its uppermost position by spring 116, the bottom end of which is secured to elevating member 52. When cam bar 54 is in this position, switch wheel 57 of hoist switch 53 is in contact with the bottom end of cam lever 55, but is not pressed by lever enough to close normally open limit switch 53. When cam roller 94 depresses cam bar 54 against the urging of spring 116, hinge 56 is also depressed to the point where notch 117 at one end of cam bar 54 rests against fulcrum 110, and notch 118 at the other end of the cam bar rests against fulcrum 112. Cam bar 54 is shown in this position in Figures 8 and 14B.

Depression of the upper end of cam lever 55 (which is rotatably attached to hinge 56) causes the bottom end of the cam lever to be raised. As the bottom end of cam lever 55 is raised, this pushes wheel 57 and causes the arm on which the wheel is borne to be rotated, thus actuating hoist switch 53.

Cam bar 54 is shown in Figure 9 in its uppermost position just before it is struck by cam roller 94. Figures 12B and 148 show how cam roller 94 depresses cam bar 54 when the roller rides upon the bar.

Figure 16 shows in plan view how cargo pallet 46, upon approaching cargo hoist 49 from the direction of the cargo accumulation station at which the pallet was loaded with air cargo, will have its cam roller 94 and guide roller directed in the correct path by guide chutes 92 and 93, respectively. Cargo pallet 46 rides upon elevating members 51 and 52. Cam roller 94 trips cam bar 54, and actuates hoist switch 53 as explained above. This causes cargo hoist 49 to raise pallet 46 into the position shown in plan in Figure 16.

Figures 17 and 18 are views of cargo hoist 50, which is at the outermost plane loading station of the system shown in Figure 1. Figure 17 shows how guide roller 104 on cargo pallet 47 is guided along the correct path by guide chute on elevating member 131 of cargo hoist 50. As shown in Figure 18, guide chute 132 occupies a corresponding position on elevating member 133 on the opposite side of hoist 50. Cam bar 102 on elevating member 133 of hoist 50 is of similar construction to cam bar 54 on hoist 49.

Personnel platform 134 is shown in Figure 18 as folded back on hinges 135 to be out of the way of cargo pallet 47 as it rides upon elevating members 131 and 133. The personnel platform is also shown folded back in end view (as seen from the direction of arrival of cargo pallet 47) in Figure 20. When cargo hoist 50 is used without cargo pallet 47, personnel platform 134 may be folded over into the position shown in broken line in Figure 19 to increase the area of the platform by about one half.

Figure 18 shows how cam roller 100 of cargo pallet 47 rolls through guide chute 132 on elevating member 133 and from there onto cam bar 102. Depression of cam bar 102 actuates hoist switch 141, in the same manner as hoist switch 53 on cargo hoist 49 was actuated by cam roller 94 of cargo pallet 46. Upright members 142 and 143 of cargo hoist 50, and corresponding upright members 142a and 143a on the opposite side of the hoist, are then raised from the down or collapsed position toward the vertical position and this raises elevating members 131 and 133 with cargo pallet 47 upon them.

Figure 21 gives a plan view of elevating member 144 of cargo hoist 48, which is located at the innermost plane loading station of the system shown in Figure 1. Cam roller 101 of cargo pallet 45 will be guided through guide chute 145 as it approaches the hoist, and will ride from the chute upon cam bar 103. Cam bar 103 is arranged with respect to its associated hoist switch for cargo hoist 48 in a manner similar to cam bar 54 of hoist 49 and cam bar 102 of hoist 50.

Consideration of Figures 9. 16, 18 and 21 discloses how the cam rollers of the various cargo pallets 45, 46 and 47 selectively operate the hoist switch means of their associated cargo hoists. The elevating members of each cargo hoist are in effect divided into lanes: three each at hoists 48 and 49, and, for convenience, two lanes at hoist 50. The cam rollers at the front of each cargo pallet (and the corresponding rollers directly behind 

